Royal Ontario Museum. Half of Toronto hate this addition, half of the city likes it. I am it the camp who hates it. Not because it is a modern building, but because it was added to an old building and destroyed its character. It is now neither here nor there. Also it is a museum, and with the glass wall it removed so much display possibilities, that a good portion of exhibits is in a storage. Daniel Libeskind is not the most practical of architects. It was voted 8th ugliest building in the 2010.
On the plus side it offers great photo opportunities.